Re: [PATCH v2 1/2] cpumask: introduce cpumask for hotpluggable CPUs
From: Daniel Lezcano
Date: Wed Aug 10 2011 - 16:53:33 EST
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On 08/10/2011 10:03 PM, Mike Turquette wrote:
> On some platforms it is possible to have some CPUs which support CPU
> hotplug and some which do not. Currently the prescence of an 'online'
> sysfs entry in userspace is adequate for applications to know that a CPU
> supports hotplug, but there is no convenient way to make the same
> determination in the kernel.
> To better model this relationship this patch introduces a new cpumask to
> track CPUs that support CPU hotplug operations.
> This new cpumask is populated at boot-time and remains static for the
> life of the machine. Bits set in the mask indicate a CPU which supports
> hotplug, but make no guarantees about whether that CPU is currently
> online or not. Likewise a cleared bit in the mask indicates either a
> CPU which cannot hotplug or a lack of a populated CPU.
> The purpose of this new cpumask is to aid kernel code which uses CPU to
> take CPUs online and offline. Possible uses are as a thermal event
> mitigation technique or as a power capping mechanism.
> Signed-off-by: Mike Turquette <mturquette@xxxxxx>
Reviewed-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
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